Fix doctests (#906)

src/transport/smtp/async_transport.rs

@@ -215,9 +215,12 @@ where
     /// ```rust,no_run
     /// use lettre::{
     ///     message::header::ContentType, transport::smtp::authentication::Credentials,
-    ///     AsyncSmtpTransport, Message, Transport,
+    ///     AsyncSmtpTransport, AsyncTransport, Message, Tokio1Executor,
     /// };
+    /// # use tokio1_crate as tokio;
     ///
+    /// # #[tokio::main]
+    /// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
     /// let email = Message::builder()
     ///     .from("NoBody <nobody@domain.tld>".parse().unwrap())
     ///     .reply_to("Yuin <yuin@domain.tld>".parse().unwrap())
@@ -228,15 +231,20 @@ where
     ///     .unwrap();
     ///
     /// // Open a remote connection to gmail
-    /// let mailer = AsyncSmtpTransport::from_url("smtps://username:password@smtp.example.com:465")
+    /// let mailer: AsyncSmtpTransport<Tokio1Executor> =
+    ///     AsyncSmtpTransport::<Tokio1Executor>::from_url(
+    ///         "smtps://username:password@smtp.example.com:465",
+    ///     )
     ///     .unwrap()
     ///     .build();
     ///
     /// // Send the email
-    /// match mailer.send(&email).await {
+    /// match mailer.send(email).await {
     ///     Ok(_) => println!("Email sent successfully!"),
     ///     Err(e) => panic!("Could not send email: {e:?}"),
     /// }
+    /// # Ok(())
+    /// # }
     /// ```
     #[cfg(any(feature = "native-tls", feature = "rustls-tls", feature = "boring-tls"))]
     #[cfg_attr(

src/transport/smtp/client/async_connection.rs

@@ -73,15 +73,23 @@ impl AsyncSmtpConnection {
     /// # Example
     ///
     /// ```no_run
+    /// # use std::time::Duration;
+    /// # use lettre::transport::smtp::{client::{AsyncSmtpConnection, TlsParameters}, extension::ClientId};
+    /// # use tokio1_crate::{self as tokio, net::ToSocketAddrs as _};
+    /// #
+    /// # #[tokio::main]
+    /// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
     /// let connection = AsyncSmtpConnection::connect_tokio1(
     ///     ("example.com", 465),
     ///     Some(Duration::from_secs(60)),
     ///     &ClientId::default(),
-    ///     Some(TlsParameters::new("example.com")?),
+    ///     Some(TlsParameters::new("example.com".to_owned())?),
     ///     None,
     /// )
     /// .await
-    /// .unwrap()
+    /// .unwrap();
+    /// # Ok(())
+    /// # }
     /// ```
     #[cfg(feature = "tokio1")]
     pub async fn connect_tokio1<T: tokio1_crate::net::ToSocketAddrs>(